President Donald Trump criticized House Speaker Paul Ryan on Wednesday after the Speaker of the House challenged his idea of ending birthright citizenship.

“Paul Ryan should be focusing on holding the Majority rather than giving his opinions on Birthright Citizenship, something he knows nothing about!” Trump wrote on Twitter.

Ryan criticized Trump’s proposal of ending birthright citizenship with an executive order during an interview on a Kentucky radio station on Tuesday.

“You cannot end birthright citizenship with an Executive Order,” Ryan said. “We didn’t like it when Obama tried changing immigration laws via executive action, and obviously as conservatives, we believe in the Constitution.”

Ryan has already announced his retirement after the Congressional mid-term elections but has campaigned for Republicans in a handful of races.

Trump said Republican Congress without Paul Ryan as Speaker would focus more on stopping illegal immigration.

“Our new Republican Majority will work on this, Closing the Immigration Loopholes and Securing our Border!” he wrote.

Paul Ryan should be focusing on holding the Majority rather than giving his opinions on Birthright Citizenship, something he knows nothing about! Our new Republican Majority will work on this, Closing the Immigration Loopholes and Securing our Border!